Stephanie Kwolek, Mother of Kevlar

While working for DuPont, Kwolek invented Kevlar.[9] In 1964, in anticipation of a gasoline shortage, her group began searching for a lightweight yet strong fiber to be used in tires. The polymers she had been working with at the time, poly-p-phenylene terephthalate and polybenzamide, formed liquid crystal while in solution that at the time had to be melt-spun at over 200 °C (392 °F), which produced weaker and less-stiff fibers. A unique technique in her new projects and the melt condensation polymerization process was to reduce those temperatures to between 0–40 °C (32–104 °F).As she later explained in a 1993 speech:“The solution was unusually (low viscosity), turbid, stir-opalescent and buttermilk in appearance. Conventional polymer solutions are usually clear or translucent and have the viscosity of molasses, more or less. The solution that I prepared looked like a dispersion but was totally filterable through a fine pore filter. This was a liquid crystalline solution, but I did not know it at the time.”[This sort of cloudy solution usually was thrown away. However, Kwolek persuaded technician Charles Smullen, who ran the spinneret, to test her solution. She was amazed to find that the new fiber would not break when nylon typically would. Not only was it stronger than nylon, Kevlar was five times stronger than steel by weight. Both her supervisor and the laboratory director understood the significance of her discovery, and a new field of polymer chemistry quickly arose. By 1971, modern Kevlar was introduced. Kwolek learned that the fibers could be made even stronger by heat-treating them. The polymer molecules, shaped like rods or matchsticks, are highly oriented, which gives Kevlar its extraordinary strength.

Applications of KevlarKwolek was not very involved in developing practical applications of Kevlar. Once senior DuPont managers were informed of the discovery, they immediately assigned a whole group to work on different aspects," she said. She also did not profit from DuPont's products, as she signed over the Kevlar patent to the company.Kevlar is used as a material in more than 200 applications, including tennis rackets, skis, boats, airplanes, ropes, cables, tires, and bullet-proof vests. During the week of Kwolek's death, the one millionth bullet-resistant vest made with Kevlar was sold. Kevlar is also used to build cellular telephones; Motorola's Droid RAZR has a Kevlar unibody.Awards and honorsFor her discovery of Kevlar, Kwolek was awarded the DuPont company's Lavoisier Medal for outstanding technical achievement in 1995, as a "Persistent experimentalist and role model whose discovery of liquid crystalline polyamides led to Kevlar aramid fibers." At the time of her death in 2014, she was still the only female employee to receive that honor.In 1980, Kwolek received the Chemical Pioneer Award from the American Institute of Chemists, and an Award for Creative Invention from the American Chemical Society. In 1995, Kwolek became the fourth woman to be added to the National Inventors Hall of Fame. In 1996, she received the National Medal of Technology and the IRI Achievement Award. In 1997, she received the Perkin Medal from the American Chemical Society. In 2003, she was added to the National Women's Hall of Fame.She has been awarded honorary degrees by Carnegie Mellon University (2001), Worcester Polytechnic Institute (1981) and Clarkson University (1997). Royal Society of Chemistry - Stephanie L Kwolek Award (2014)The Royal Society of Chemistry grants a biennial 'Stephanie L Kwolek Award', "to recognise exceptional contributions to the area of materials chemistry from a scientist working outside the UK".RetirementIn 1986, Kwolek retired as a research associate for DuPont. Toward the end of her life, she consulted for DuPont, and served on both the National Research Council and the National Academy of Sciences. During her 40 years as a research scientist, she filed and received either 17 or 28 patents.Kwolek died at the age of 90 on June 18, 2014.